Automatic telephone switch and system



D-. S. .HULFISH.

AUTOMATIC TELEPHONE SWITCH AND SYSTEM.

APPLICATION FILED DEC. 8, I917.

Patented Aug. 29, 1922.

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AUTOMATIC TELEPHONE SWITCH AND SYSTEM.

APPLICATION FILED DEC. 8,1917. Patented Aug. 29, 1922.

6 SHEETS-SHEET 2.

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D. S. HUL F|SH. AUTOMATIC TELEPHONE SWITCH AND SYSTEM.

APPLICATION FILED DEC. 8, 1917- 1 ,427,473, Patented Aug. 29, 1922.

6 SHEETS-SHEET 3.

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APPLICATION FILED DEC. 8. I917. 1 ,427,47 3, Patented Aug. 29, 19.22.

6 SHEETSSHEET 4.

D. S. HULFISH.

AUTOMATIC TELEPHONE SWITCH AND SYSTEM.

APPLICATION FILED DEC-8,1917.

6 SHEETSSHEET 5.

DAVID S. HULFISH, OF TORONTO, ()NTARIO, CANADA.

AUTOMATIC TELEPHONE SVi ITCI-I AND SY$TE1VL Application filed December 8, 1917. Serial No. 206,189.

To all to 7mm it may concern Be it known that 1, DAVID SrrnRmLLHUn FISH, a citizen of the United States of America, residing a llloronto, in the county of York and Province of Ontario, Canada, have invented new and useful Improvements in Automatic Telephone Switches and Systems, of which the following is a specification.

My invention relates to improvements in automatic electrical switches and in the uses thereof, and the objects of my invention are to provide an improved power-driven electrically controlled switch, improved circuit systems for connecting the switches for service, and improved methods of operation, as illustrated i the accompanying drawings, and as described herein.

In the drawings: Fig. 1 shows section oi switch and tag bank on line 1-1 of Fig. 2. Fig. .2 shows front elevation of switch with tag bank omitted. Fig. 3 shows driving devices. Figs. 4c, 5, 6, Y and S unite to form a large circuit diagram, and show a system of circuits for giving telephone se ice. Fig. 9 shows an amplification of par-s; oi the circuit diagram.

Referring to Figs. 1 and 2: The movable brushes 201, 202 carried by insulation upon brush shaft 203 engage the under surfaces of eligible tags 204i, held lined in the tag bank upon insulating plate 206. tag bank: comprises a plurality of levels of tags, many known methods of construction being available. Each level has two brushes as shown, each brush having a "feed tag 205 fixed in the tag banlr. The :Feed tags are in the level 01'? the eligible tags. The brushes shown, 201 and 202, engage the under surfaces of the feed tags as well as of the eligible hence the brush may pass the feed tag. Alternate levels have brushes above instead oi below. The tag bank comprises tag-bank.- plates 206 i and tags 204, 205, rigidly held together and attached to tiring plates 20?, the fixing plates being then lined upon vertical snpporting rack bars 208. Dowels 255 are fixed in part 201 and pass through holes in switch body-plate 209. The faces oi parts 20? eng the back face of part 209.

Body plate 209 has. flanges 210 support ing brush carrying shaft 203 and armature shaft 211. The brush carriage comprises The shaft 203, hub 212, ratchet 213, brush spacers 21d of insulation, feed-tag guides 215 of insulation, brushes 201, 202, clamp 216, and screws 21'? which thread into hub 212 and clamp all parts. The alinement of brushes is attained by insulating dowels 218.

Main spring 219 attached to hub 212 and flange 210 turns brush carriage when double pawl 220 permits and brushes pass from tag to tag, advancing a half-step when armature 221 has been attracted and the remaining half-step when armature has been returned to normal by armature spring 256. A brush may be shaped to engage a tag while the ari'nature is normal or while the armature is attracted, or both. A brush at one end of its travel may rest upon its own "feed tag. Armature carrier 222, carrying armature 221 and double pawl 220, is carried by armature shaft 211 between spacing sleeves 223, and is pulled by spring 256. lliagnet support 22-l supports magnets 225 and clutch-arm guide 226. Clutch arm 227 is pivoted upon ratchet 213, rests upon wing 228 of guide 226 and is drawn against the guide by spring 229. Clutch tooth or thrust member 230 is. clamped upon drive shaft 231. Drive shaft 231 oscillates continually through predetermined angle. Normal switch comprises two contact springs mounted upon bracket 233 upon supporting bar 208, tending to open, held closed by part 226 and spring 234-. Clutch arm 22? is shown in three positions, solid line in normal position, dash line awaiting restoration, and dot-dash line at close of thrust of clutch hook. Parts 230 and 236 are shown in dot-dash line in their positions at the time part 227 occupies its dot-dash position. I

The operation of the switch is as follows: Repeated electrical currents through magnets operate armature 221 repeatedly and brush carriage moves step-by-step until a desired selective position is attained. For restoration to normal, further repeated or intermittent currents operate armature, brush carriage moves, clutch arm 22?, propelled by ratchet 213, passes its corner 235 beyond guide spring draws clutch arm into path of clutch tooth 230, as shown in dot line in Fig. 2. The clutch tooth engages the clutch arm and forces the clutch arm to the position shown in do dash line in Fig. 2, thus restoring the brush carriage to normal. The clutch-arm corner 235 has forced guide 226 to position shown in dot-dash line, thus opening normal switch 232 as shown in dot-dash line. Tooth 230 retires and disengages itself from arm 227, spring 23% pulls guide 226 to normal position, closes normal switch 232 and lifts arm 22? to normal position as shown in solid line. By determining the dimension of the double pawl 220 between the faces which engage the ratchet, the relative lengths of the first and second steps of the ratchet and brushes for each ratchet tooth may be determined.

The devices for driving the shaft 231 are as follows: Motor 236 (Fig. 3) drives power wheel 23?, link 238 and driving arm 239 upon shaft 231. The shaft 231 oscillates continually as indicated by the doublehead curved arrow.

Switches of the type described may be organized by electric circuits and associated with telephones and callsenders to give an automatic telephone service. A system of circuits is shown in Figs. 4, 5, 6, 7 and 8, the figures uniting at the margins where conductors of similar labels meet. Each switch has tag-levels suiilcient in number for its requirements, the levels being numbered at the ends. The tags in each level are numbered below. Each tag is represented by a circle; each brush by a rectangle united by conductor-line to its feed tag. Brushes shown between tags will engage the tag at the half-step. The callsender may be of any known type, the electrical contact members being arranged as required.

In the drawings, numbers under 100 are location numbers for identifying contact tags. A tag is identified by giving first the label of the switch, then the level number, then the tag number in the level; thus, 1032-6, meaning switch 103, level 2, tag 6. A brush is identified by the location of its feed tag. Switches 101 and 105 have some of their levels omitted from the diagram. Switch 101 engages its clutch members for mechanical restoration when its brushes reach tags 13and25, th brushes then being restored to tags 1and- 13. Switches 102, 104C and 105 restore from 12and-24 to 0and-l2. Switch 103 restores from 11and-23 to 0and-12.

The automatic switches are grouped into sets or divisions, which are duplicated as required to serve the trafiic. A set of switches comprises pilot 103, groupfinder 102, linefinder 101, register 104 and final connector 105.

Each telephone line has two relays, line relay 1&9 and cut-oft relay 148. The line relays pertaining to each searching brush of the linefinder 101 have a common wire 305 to the groupfinder, identifying the linefinder group among the groupfinder tags. Circuits are referred to by numbers, C1, C2, and so on.

The operation is as follows:

A lifted receiver at telephone 106 by its hookswitch closes C1 and charges telltale relay 1 17, line relay 148 and starting relay 1 16.

0]. Line oircuit.(Pilot brushes on tags 1and-13). Battery, helix of 1&7, points of 1 1-8, linewire 301, telephone 106, linewire 302, points of 1 18, helix of 149, helix of 146, earth.

Starting relay 1 16 closes C2 to charge groupfinder magnet 122 repeatedly as S2 is interrupted repeatedly by brush 102d25 at the half-step, until brush 1021-25 closes searching circuit C3. C3 then charges test relay 138 which opens C2 and closes C 1 to advance the pilot. brushes to open both C2 and C3, the relay 138 hen opening C 1. The pilot brushes pass to tags 2and1t.

U2. Groupfinderdroe. (Pilot 1-13). Battery, groupfinder magnet 122, normal switch 112, interrupting brush 102at-25 and tags 12-to 22, wire 324., 103-513, wire 35 1-, points of 138, wire 3 14, 103-4- 13, wire 306, points of 1&6, earth.

Groupfindcr tcsz (l?ilot 113). Battery, helix of test relay 138, wire 350, 103213, wire 327, brush 102125, tag 102-1 1a or analogous tag identifying the line-group containing the calling line, wire 305, points of 1419, earth.

U4. iPiZot 92mg"uct.-(Pilot any position). Battery, pilot magnet 123, normal switch 113, wire 319, points of 138, earth.

With pilot brushes on tags 2-and-1 1, starting relay 1&6 closes C51- and then C5 to charge linefinder magnet 121 repeatedly as C5 is interrupted repeatedly by brush 1012025 at the half-step, until brush 101-17-0, (or analogous brush selected by the groupfinder, the several eligible sets of tags in 102 being connected to brushes on eligible levels in 101 in manner analogous to tags in the eligible set 102 1 2, 102 2 2, 102-3-2, 1.02 i---2,) engages wire 36 1 of the calling line on tag 101 20 at and closes searching circuit C6. C6 then charges test relay 138 which opens C5 and closes C l again to advance the pilotbrushes to open both 05 and C6. The pilot brushes pass to tags 3and15, and charge the cutoff relay over C7.

05;}. le'nefimle r cZri'vc.-(Pilot 214). Battery, linefinder magnet 121, normal. switch 111, brush 101 2025, 101- 20-13, wire 616, 1031-1 1, wire 354-, points of 138, wire 3 14, 103-%--1 i, wire 306, points of M6, earth.

U5. .Einefinclcr drive. (Pilot 214). Battery, linefinder magnet 121, normal switch 111, brush 1012025 and tags 1 tO-2t, wire 325, 103514, wire 354:, points of 138,'W1I6 3 1et,103-4 1, Wire 306, pointsof 1 16, earth.

06. Linefiader nestle-(Pilot 2-1/1). Battery, helix 01-138, Wire 3:30, 103214L, Wire 326,-brush 102-- 0 and tag to which that brush has been adjusted, brush 102 200 moving until Wire 30 1 of calling line is engaged upontag 101-20 1-, 'wire 36 1, points of 1 19, earth.

0?. Calling guaml.(l?ilot 3'--15 to 6--18). Battery, resistance 13 1, 1036--3, Wire through 102 and 101. as ed to Wire 363, helix of 1 18, earth.

lVith pilot brushes on tags 3and-15 a loop C8 is formed to the calling telephone through signal relay 14:1 and holding relay 1 1-2, charging those relays.

U8. (Yelling Z00p.-(Pilot 315). 13sttery, helix of 1 1-2, Wire 336, 103- 13, Wire 311, through 102 and 101 as adjusted to Wire 361., linen-ire 301, callsender conductor springs 151, 152, telephone 106, linewire 302, Wire 362, through'lOl and 102 as adjusted to Wire 312, 1035 3, Wire 3 10, helix oil 141, earth.

The next action is to adjust the register or tens switch 104 to the selective position required to select ultimately the desired line to be called, by action or the callsender at the telephone, and then to shift the pilot brushes as a changeover switch.

The callsender When operated moves 150 to engage 151 andto disengage 1511mm 152 a predetermined number of times, meanwhile holding shunt switch 151 closed during the entire operation. Each movement of 150 forms a circuit to earth (18-1- to hold holding-relay 1 1-2 and then brealts C8 to release signal relay 1 11; Signal relay 141 thus is released several times rapidly to effect the adjustment of tens switch 10 iand changeover of pilot 103.

To adjust switch 1041-, relay 1-1-1 closes C9 repeatedly. To shift switch 103 at the end of adjustment of 104:, relay 1 sends by C10 a set of impulses to end-signal re lay 139 and switch 104 also sends by G101 a set of impulses to relay 139, the two sets of impulses being concurrent but out of phase so that the points of 139 are held operated until after impulses cease-in U10. lVhen 139 is finally released, it closes C11 to charge relay 138 which in turn closes C-l' again to advance the pilot brushes. r-ln impulse in C10 ceases when 1 11 is re-charged but the companion impulse in G101 con tinues until-12 1 in G9 has been magnetically discharged, until. the armature 219 01' 12- has been released and retracted to permit dog 2-20 to clear from the tooth of ratchet 213 and until niainspring 219 has moved. the brushes as a mass so :tar that brush 104i-6-0 has broken contact from this succession in time in the termination of the tWo companion impulses 1 am describing briefly by saying that the impulses are concurrent but out of phase. The two re.-

lays 14-1 and 139 are preferably alike in mechanical construction, the delay by phase displacement of the impulses to 139 being sucn that in a series of signers tell is re-discharged to re-charge 139 before 139 can close C11.

Wire 318, tags and brush 10el-50, Wire 319 points of discharge 139, earth.

Pilot brushes pass to 1-and16 and prepare circuits for the adjustment of the final connector or units switch, 105, the circuits being C12, C10, @102 and C13, and the action being analogous to the action in adjusting switch. 10 1-. Callsender spring 151 discharges 1 -1-1 repeatedly. Relay 1 1-1 sends impulses by C12 to magnet 125 and by C10 to relay 139, concurrently with impulses sent by C102 from switch 105 to relay 139. Relay 139 then closes changeover circuit C13 through switch 105 to shittswitch 103. (7113. Units impuZses. Pilot 4-10}.

Battery. final connector magnet 125, normal switch 115 Wire 103616, wire355,

points oi discharged 1411, points of charged 1-1-2, earth.

(170,2. .EuosgnaZ an; 16).- Battery, lower helix of 139, Wire 31?, 10310- 1-, Wire 399, brush 10520-0 and tags 1 to 11 at halt-step, and to earth over Wires 30? and-304a.

(715. Emlsymzl.(Pilot 1- 10). 'Battery, helix of 138, \vire 103-21(3, wire 370', ii: l

points of discharged 139, earth. llelay 138, charged by C13, closes C: again and passes pilot brushes to i3 and-17. The selected being not busy, the uncharged busy-test relay 13? charges relay 138 by @1 1- and 138 by passes tags 6*and18 Where 1 71315 the cut-oil relay 101'- of the selected line charged. 1

C14 Idle test.(Pilot 517). Battery, helix of wire 350, 1032--1Z, wire 375, points of 137, who 615, secondary Winding of tone induction coil 136, earth.

brush 105190, Wire ringing key at the calling telephone. By

earth upon wire 301, C83,- is formed to hold *relay 1 12 and relay 141 is shunted and releases its armature, closing C16 to charge ringing relay 144-. Ringing relay in closes C1? to connect ringing generator 1 15 throu 'h the selected line.

b v C16. Rang mg rc!/(4 1/.(11lot S 18).

Battery, helix of 14 1, points of charged relay 14:2, wire 37?, 103618, wire 355, points of discharged 1 11, points of charged 142, earth.

(717. Hingng.-(Pilot 618). Ringing generator L15, wire 609, points of 144, wire 338, 103-10, wire 321, through 101 and 105 as adjusted, to wire condenser and callbell of telephone 108, wire 352, switches 105 and 1 as adjusted, wire 322, 103-2-6, wire and through helix of 141-0 to first earth; branching from wire tl'irough wire 318, condenser 132, wire 38%, 10380, 103-8-0, 10350, and wire 3 10 and helix of 11-1 to second earth branching from 1035-0 through 103-56, wire 312, switches 102 and 10.1 adjusted, wire 302, wire 302, calling telephone hookswitch, wire 301. switches 101 and 102 as adjusted. wire 311, 103--1-G, 103- 10, wire helix of 142 to battet-fy and to third earth; branching from 103 1--0 through 1037-6, wire 385, condenser 131. wire 3 17 helix 01141-3 to battery and to fourth earth.

Lifting the receiver upon the selected line closes a loop G18 through answering relay 1&0 and answering teed spool The circuit for speech transmission C19 is over con ductors of C8 and Q18 through condensers 131 and 132.

018. Answering Z00p.(1 ilot 018). Battery. helix: of 1 13, points of 14-4, thence over C17 to first earth.

019. .Spea/xring.(Pilot 6--18). Includes C8 and C18, except 14:0, 141, 142, 1 13, and connected together as follows: From 103-5-0, through 103-80, wire 384, con denser 132, wire 948 to wire 33?; and from 10/1-0,througl 103'?-6, wire 385, condenser 131, wire 34?, points of 1 14 and to wire 338.

I divide the action of the automatic switches into two parts. first, operation. by which a telephone call is given servi. and second, restoration, by which used switches are returned to their normal condition of waiting, in readiness for service upon subsequent call.

In using the switches herein described, the method of restoring each switch is to advance the switch electrically to its ultimate position, then to engage its mechanical power source and to restore it mechanically to its primary position. If all switches were restored simultaneously, C7 and C8 might be formed to certain lines through switches 103, 102, 101, while C15 and C18 might be formed to certain lines through switches 103, 101, 105, all or" which might be found objectionable. To obviate this conrlition, I provide a method of restoring in which all switches are rendered independent in their operating circuits but dependent in certain restoring circuits, then are restored serially or in groups in such order and in such manner that no operating circuit is formed to any telephone line during the action of restoring, and ultimately are rendered again electrically dependent in their operating circuit by the final act of restoration. In this method of restoration, the circuits in each switch which might lead to telephone lines are held open in a second switch while the prime switch is returning to normal.

The calling telephone line initiates the release ef the switches by hanging the receiver upon the hook, breaking C8 and releasing holding relay 142 which by its points closes C20 to advance the pilot brushes. C20 char es relay 138 which by C4 charges pilot ma net 123. The pilot brushes leave tags 6-and18 and break all operating circuits.

0930. Pilot "-eZ@ase.(Pilot in any position from 315 to 921). Battery, helix of 138, wire 350, brush 103-325 and tags to wire 360, points of 142, earth.

The circuit C20 is interrupted at the halfstcp on brush 103-3-25 and the pilot brushes advance to tags.10and-22, where C21 advances thelinefinder 101 to position 13-and-25 and C22 advances switches 102, 101. 105 to position 11and23 in each switch. When brushes in switches 102, 104, 105 have reached tags 23, occupying then their sub-restoring positions, they close C23 which charges relay 138 which by C 1 advances the pilot brushes to tags 11and-23.

2]. Lc'nefincler reZease.(Pilot 10- 2). Battery, lineiinder magnet 121, normal switch 111, brush 1012025' and tags 14 to 21-, wire 325, 103822, earth.

0 Switch. 1-eZease.(Pilot 10-22). Battery, final connector magnet 125, normal switch 115, brush 105-20-25 and tags 13 to 22, wire 308, 1031022, earth. Also, battery, register magnet 124, normal switch 114;, brush 101-6-25 and tags 13 to.22, wire 315, 103-9-22, earth. Also, battery, groupiinder magnet 122, normal switch 112, brush 102- 125 and tags 12 to 22, wire 321, 103-7-22, earth. If switch 104: has not been operated from normal C22 will not opera-te that switch. if switch 105 has not been operated from normal, C22 will not operate that switch.

Pilot cZutc/1i.(Pilot 1.0-22). Battery, helix of 133, wire 350, 1033--22,

wire :ne, 105-17 2a, wire 10414423,

wire 336. and earth over wire 323. If switch 104- has not been operated from normal, C23 will be through l04.--2 12. It switch 105 has not been operated from normal, will be through l.0517 12.

in the linefinder 101, with brushes on tags 13-and--25, shoulder 235 passes memher 226 and 227 awaits engagement of 230. In the pilot 103, with brushes on tags 11- and-23, shoulder 235 passes member 226 and 227 awaits engagement of 230. This difference may be attained by variant lengths of arm 227 on the sundry switches and. by adjusting the angular position of guide 226. W ith the next advancing swing of shaft 231 and hooks 230, the linefinder 101 is restored to its normal position with brushes on tags 1and13, while the pilot 103 is restored mechanically to a prenormal position beyond its electrical normal position, and stops with its brushes on tags 0 and-12. During the reverse movement oi the linefiner brushes, no circuit is completed to any line, because I do not connect any linefinder brush touching a telephone line wire to any groupfinder tap, upon which a groupfinder brush rests, tags 102111, 102-2-11, 102311 being left vacant. During the reverse movement of the pilotbrushes, no circuit is completed to any line in the final connector, because switches 10 1 and 105 are motionless and 1 arbitrarily leave vacant in the final connector switch the tags to which conductors 311, 312, 313 are extended in that adjustment of switches 104 and 105. Thus, during the reverse movement of 101, its telephone-line-wire circuits are open in 102; during the reverse movement of 103, its line-wire circuits and its guard-wire cir cuits, which alone can influence any telephone line conductor, are open in 102 and 105; during the ensuing reverse movement of 102, 104, and 105, their line-wire circuits are open in pilot 103 with its brushes on tags 0--and12.

Pilot brushes on tags 0-and-12 close C24 and switches 102, 10 1, 105 advance their brushes one step, engage their clutch member upon the next swing of the clutch hooks, and return to normal positions shown. in the drawings, closing then C25 which by C4 advances the pilot brushes to position 1and-13 and completes restoration, the switches becoming again electrically depend ent for operating circuits and being again in readiness for further service in response to a calling telephone line.

0%,. Switch 0Zatch.( Pilot 0-12). Battery, final-connector magnet 125, normal switch 115, 105--20-23, to wire 330; also, battery, register magnet 12%, normal switch 11 1, 10 1-65-23, to wire 330; also, groupfinder magnet 122, normal switch 112, 102 l23, to wire 330; then wire 1031012, earth. It 1041- or 105 has not been operated from normal, does not operate that switch. i

(725. Pilot n0rmo-Z ing.(Pilot 012). Battery, helix of 13S, wire 350, 1.03-2- 12, wire e35, 105 1s 12, 1O4'i3-12, wire e14, 1023-12 and to earth over wire Should the selected line he found busy, potential will be found upon wire with pilot brushes on tags 5-and17, and current over C26 will charge busy-test relay 137, thus preventing the operation of C14. Filot brusnes will remain on tags 5and17 until the receiver of the calling telephone is hung up. Relay 137 will close C271} to operate buzzer 135 and also will close C27 by which the buzzer tone currents are carried to the calling telephone.

When the busy-test relay has been operated, a locking circuit C26 with auxiliary release circuit C20} in pilot position 618 prevents the pilot 103 from stopping in speaking position upon that call.

026. Busy test.-(Pilot 517). Bat tery, any resistance 134 or 17 1-, wire 353, switches 105 and 10 1- as adjusted, wire 323, 103-3-5, wire 376, helix of 137, earth.

02711. Tone primary.-(l ilot 5-17 Battery, helix of 135, points of 135, primary helix of induction coil 136, wire 396, 103717, earth.

U27. T0ne.(Pilot 517). Earth, secondary helix of 136, wire 615, points 019137, wire 340, then over CS through helix of? 14:2 and battery to earth. 0261;. Z0c7cing. (Pilot 517). Ba tery, lower helix of 139, wire 317, wire 617, tag and brush 101-17-25 in lineiinder as adjusted, wire 608, points of 137, helix of 137, earth.

0201 Bus-yreZeas@,(Pilot 6-18). Battery, helix of 138, wire 350, 103-218, wire 61-1, points of relay 139, earth.

The pilot lamp 1% glows to show an operating division while its brush is upon tag 1 1-, 15, 16 or 17. YVith the brush on 18, the ringing lamp 195 glows while the relay 1 10 is uncharged by reason of the receiver of the selected line being on the hook. Pilot lamp 194- glows while its brush moves over tags 19, 20, 21, while its brush waits on tag; 23, and while its brush waits on tag 12, thus giving an intermittent signal during" restoration of the division The calling loop circuit C8 is closed preto 103--5.2 while the pilot is in position giving the relays 14-1, 14-2 a pre- Y magnetization and avoiding slow upon a line loop oi high resistance. thus described my invention, what im as new and desire to secure by States Letters Patent is:

combination, an electrical switch, may for said switch, means for propelling said switch controlled. by said mag nets, a prime mover supplying power for restoring said switch, and mechanical means operated by said prime mover independent of electromagnets for preventing the energization of said magnets during the restoration of the switch.

2. In an automatic telephone system, a callsender adapted to create a series of electrical impulses; a switch controlled wholly thereby; a magnet 139 having a. first control by impulses from said callsender; and turther means, comprising in part parts in Said switch, for exercising a secondary control upon said magnet, said magnet controlled contemporaneously from both said callsender and said furthermeans.

In an automatic telephone system, a callsender generating a series of electrical currents; a switch controlled by said callsender: circuit closed repeatedly by control of said callsender a second circuit closed repeatedly by control of said switch; and a magnet 139 containing in its helices portions of both circuits said circuits controlling said magnet at times contemporaneously.

4. In an automatic telephone system, a callsonder generating a series of electrical currents; a switch controlled by said callsender: a circuit closed repeatedly by control of said callsender; a second circuit closed repeatedly by control of said switch; and a changeover device containing a portion of each of said circuits, said circuits effective at times contemporaneously.

5. In an automatic telephone system, a calsender; a selective switch: a changeover device; circuits from said callsender to said selective switch and circuits from said call sender to said changeover device whereby said callsender sends to said switch electrical impulses to operate said switch selectively and whereby said callsender sends to said changeover device electrical impulses for primary control of said changeover device; said switch having trill-step positions of selective adjustment and having half-step positions intermediate of its positions of adjustment; and a further circuit closed by said switch in its halt-step positions whereby said switch. sends to said changeover device electrical impulses for secondary control of said changeover device.

6. In an automatic telephone system, a callsender, a selective switch; achangeover device; said selective switch having selective positions of adjustment and having stop positions intermediate of its positions of adjustment when its brushes are at the halt-step; and a circuit "from said switch to said changeover device and preventing the operation of said changeover device while said switch is in an intermediate position.

7. In an automatic telephone system, a callsender; a selective switch having selective positions and halt-step stop positions; a changeover device; and means for preventing the operation of said changeover device while said switch is in a. halt-step position.

8. In an automatic telephone system, callsender; a selective switch having selective positions and halt-step positions; a changeover device; circuits from said callsender to said switch whereby said switch is advanced to half-step position by the beginning of a current under control of said callsender and whereby said switch is advanced from the halt-step position by the cessation of a current from the callsender; a circuit from said switch at half-step to said changeover device and broken by said switch when leaving its haltstep position, whereby current in said lastcircuit continues after cessation of current in said first circuits.

9. In an automatic telephone system, a callsender; a selective switch having selective positions and half-step positions; a changeover device; circuits from said callsender to said switch whereby said switch is advanced to halt-step position by the beginning of a currentunder control of said callsender and whereby said switch-is advanced from the haltstep position by the cessation of a current from the callsender; a circuit from said. switch at halt-step to said changeover device and broken by said switch when leaving its half-step position, whereby current in said last circuit continues after cessation of current in said first circuits; and further circuits from said callsender to said changeover device.

10. .ln an. automatic telephone system, a callsender and circuits in combination to produce a series of signal currents; a switch and circuits in combination to produce a second series of signal currents, said switch controlled by signal currents from said callsender, said second ries of currents being concurrent with said first series of currents and the currents of said second series being out of phase with the currents of said first series; and a changeover device controlled by currents of both series concurrently.

11. In an automatic t lephone system, a callsender and circuits in combination to produce a series of signal currents; a switch and circuits in combination to produce a second series of signal currents, said switch controlled by signal currents from said callsender, said second series of currents being concurrent with said first series of currents and the currents of said second series being out of phase with the currents of said first series; a changeover device controlled by currents of both series concurrently; and a changeover circuit prepared through contacts in said selective switch and closed ultimately by contacts in said changeover device.

12. In an automatic telephone exchange. selective switches and a pilot switch. said pilot switch having a pre-normal position; contacts in normal positions of said selective switches, respectively; and a normaling circuit for the pilot by which the pilot may be advanced from pre-normal position to normal position only when the said selective switches are in normal positions.

13. In an automatic telephone exchange,-

a division of switches containing selective switches and a pilot switch, circuits for advancing said selective and pilot switches to sub-restoring positions; a circuit controlled by the selective switches in sub-restoring po sitions to advance said pilot switch; i leans for restoring said pilot to pre-normal position circuits closed by said pilot in pre-normal position to advance said selective switches; means for restoring said selective switches to normal; and a circuit through said selective switches when normal to advance said pilot to normal.

14:. In an automatic telephone exchange, division of switches containing linefinder, groupfinder and pilot; circuits for advancing said switches for restoration, and means for restoring the groupfinder after the pilot and linefinder have been restored.

15. In an automatic telephone exchange, a division of mechanically similar switches containing linefinder, groupfinder and pilot; circuits for advancing said switches for restoration; and means preventing simultaneous restoration of groupfinder and pilot.

16. In an automatic telephone exchange; lines; selective switches containing terminals of said lines; a pilot for said selective switches; conductors between the pilot and the selective switches; circuits for advancing said selective switches to positions where said conductors are disconnected from any of said lines; means for restoring said pilot by reverse movement while said conductors are disconnected.

17. In an automatic telephone exchange; lines; selective switches containing terminals of said lines; a pilot for said selective switches; conductors between the pilot and the selective switches; circuits for advancing said selective switches to positions where said conductors are disconnected from any of said lines; means for restoring said pilot by reverse movement while said conductors are disconnected; and further means for restoring said switches by reverse movement while said conductors are open in said pilot.

18. In an automatic telephone exchan e, a pilot SR ch operable through a plurality of positions incl busy-test position and speaking on; busy-test relay; a second relay; :1 locking circuit for said two relays: and a release circuit for said pilot from speaking position and formed by said second relay when locked by said busy-test relay.

19. In an automatictelephone exchange, a pilot switch. a pilot-lamp, a lamp circuit having in the pilot swit ing said lamp to give continuous glow in each position of the switch when setting up a connection; and ther circuit connections in the pilot switch for causing said lamp to glow intermittently curing the actions of release and restoration of the pilot switch.

20. In an automatic telephone system a pilot switch constituting change over device; changeover relay co-operating with said pilot switch to produce changeover; a numerical switch; a callsender; circuits controlled by said callsender to said relay and to said numerical switch; a circuit controlled by said. numerical. switch to said relay; and a circuit through contacts of said relay and said numerical switch to said. pilot switch.

21. In an automatic telephone system, a pilot switch constituting a changeover de* vice; a changeover relay co-operating with said pilot switch to produce changeover; a numerical switch; a callsender; a signal relay controlled by said call sender circuits controlled by said signal relay to said changeover relay and to said numerical switch: and a circuit controlled by said numerical switch to said changeover relay; the currents in said two circuits being concurrent but out of phase.

22. ln an automatic telephone system antomatic switches each having a tag bank and a set of movable brushes, said brushes having normal and offaiorinal positions; a starting circuit for said switches; normal tags in each switch through which when said brushes are in normal position, said starting circuit may pass to apparatus associated with said switch: and other tags in each switch. through which said circuit may be continued independently of apparatus associated with said switch when said brushes are in certain position other than normal. said switches otherwise independent. I

ln an automatic telephone system. a telephone line; rel ys responsive to currents over said line; an automatic switch; and a short circuit between utomatic switch elements and causing initial charge of said relays betore said relays are connected to said line.

24;. In an automatic telephone system, a

h connections for cans telephone line; relays responsive to currents over said line; and a circuit over conductors local to the central oiiice and providing a path {or current through. said relays for initial cha before said relays are connected to said 1 lie.

In combination, a prime mover, a shaft driven by said prime mover; switches; circuits for advancing said switches; parts in said switches for engaging said shaft for restoring said switches, said parts opening said circuits in each switch being restored.

26. In combination, a prime mover, switches, a power shaft associating said prime mover with said switches; means for restoring a switch by said prime mover; a

circuit for advancing a switch, said circuit being rendered inoperable by said prime mover during restoration of said switch and until after disengagement of said. prime mover from said switch after restoration.

27. In combination, an electrical switch comprising fixed parts and a movable brush carriage; a main spring propelling said brush carriage in its movement of selection; a power shaft, and a single power-transmitting link connecting said shaft and said brush carriage at times to restore said brush carriage.

Signed by me at Toronto, county of York, and Province of Ontario, Canada.

DAVID S. HULFISH. 

